1. Field of the Invention
The present invention relates to a method for determining the remaining service life of a vehicle component of a vehicle, in particular a railway vehicle, operated on at least one predefined track section of a track network, wherein the remaining service life is determined for a vehicle component of the vehicle mechanically stressed by the interaction between the vehicle and the track section, after a usage interval of the at least one track section. The remaining service life of the vehicle component is determined from a prior loss of service life preset at the beginning of the usage interval for the vehicle component and from a current loss of service life of the vehicle component associated with the usage interval. The invention further relates to a corresponding system for determining the remaining service life of a vehicle component. Finally, it relates to a measuring vehicle, which supplies corresponding measurement values for determining the remaining service life of such a vehicle component.
2. Description of the Related Art
The components of vehicles, in particular such vehicle components which are subject to dynamic stress, are typically designed in respect to their endurance limit for a certain service life that can be preset. Typically, for this design, theoretical stress to be expected on the vehicle component is estimated in conjunction with corresponding safety factors. The theoretical stress to be expected in this case typically results from a conglomerate composed of empirical values from different load cases, which may occur in operation of the vehicle.
Since, during the development of the vehicle, typically no detailed assertions can be made about the later actual loading of the vehicle and thus the actual stresses on the vehicle components, usually extreme load cases have to be considered (though they rarely arise, but are nevertheless theoretically possible) in order to avoid premature failure of the vehicle component should such extreme load cases actually occur. In particular with safety-relevant vehicle components, correspondingly high safety factors are usually also applied. Commensurate rules for designing the vehicle components are frequently stipulated by law or (in particular in connection with public passenger and freight traffic) by regulations of the vehicle operator.
Thus, for example, railway vehicles are dimensioned according to international regulations and technical specifications with respect to their strength and safety requirements. Related to the strength these are the loading and load changes which the vehicle has to withstand without damage over its service life. Running safety certifications are established on the basis of a defined track situation and the vehicle parameters. In the case of all observations, the interaction between track and vehicle is crucial as to whether the certifications maintain their validity. If, due to deviation of the track situation as a result of increasingly poor maintenance, the loading changes and/or the amount of loading alter, then this leads to the possibility of damage to the components, in particular the bogies, occurring in the form of cracks, before the end of the planned service life. Cracks represent an operating risk which usually requires very costly inspection of the vehicle components (with crack control) of the vehicle fleet so that it can be kept in operation (possibly after damaged components have been replaced).
In view of this, a maximum theoretical service life is usually specified in the form of a certain maximum operating performance distance (for example in kilometers traveled or the like) for vehicle components which are subject to dynamic stress due to the interaction between the vehicle and the track on which it runs. From the operating performance consumed by the vehicle at a certain time (for example the kilometers traveled so far), the remaining service life of the vehicle component concerned is then usually estimated as the difference between the maximum operating performance and the operating performance actually consumed.
The problem here is that a vehicle is actually subjected in operation to a conglomerate of load cases, which perhaps substantially deviates from the theoretical conglomerate of load cases assumed during its development. Therefore, a vehicle component may have been subjected over its previous usage period both to substantially higher and substantially lower stress than was assumed during its development.
Thus, on the one hand, cases may arise wherein the actual service life of the vehicle component has not yet been reached (the vehicle component could thus continue to be used quite safely) although the theoretical service life (for example in the form of a maximum operating performance) is reached. This is not critical from a safety point of view; however, from an economic point of view it is disadvantageous for the operator of the vehicle.
If the end of the theoretical service life has been reached, for example, the vehicle component concerned must usually be replaced or it must be checked whether the theoretical service life of the vehicle component can be extended. While calculation of the remaining service life of a vehicle component subjected to visible wear and tear usually entails comparatively few problems, vehicle components without such visible wear and tear frequently have to undergo very costly non-destructive testing.
The situation is considerably more critical if the vehicle component is subjected in actual operation to stresses, which are considerably greater than those which were used during its development. In this case, the possibility exists that the actual service life ends, that is to say the vehicle component fails, before its theoretical service life has been reached. In particular in the case of safety-relevant vehicle components that are not subject to wear and tear which can be easily detected, such situations must be avoided at all cost.
An important factor of influence for the loads actually arising during operation of the vehicle and the stresses on the vehicle components resulting therefrom is the condition of the track, on which the vehicle is operated. In order to record this condition, it is known from WO 00/70148 A1 and U.S. Pat. No. 5,579,013, for example, inter alia to arrange acceleration sensors and distance sensors on the vehicle in order to record the interaction between the vehicle and the track and to draw conclusions about the condition of the track. Although with the data concerning the track gathered in such a way, needs-based planning in respect to its usage or maintenance can be carried out for the latter. However, this does not provide a method to solve the aforesaid problems in connection with determining the remaining service life of vehicle components.
In U.S. Pat. No. 5,579,013 it is also proposed to draw conclusions about the condition of certain components of the vehicle, for example the wheels, from the measurement signals of the sensors. Although it is therefore possible to detect damage to certain components which, on the one hand, have measurable influence on the dynamic condition of the vehicle (consequently therefore have corresponding influence on the measurement values of the sensors used), damage which entails no such dynamic influence cannot be detected.
Therefore, the object of the present invention is to provide a method, system and measuring vehicle of the kind specified initially, which overcomes the drawbacks mentioned above and in particular enables the remaining service life of vehicle components to be determined more simply and at the same time with sufficient precision at arbitrary points in time.